LENGTH
1 in. 1 mm. 1 ft
1 meter
1 micron
12 inches
3 feet
5280 feet
6080 feet
1 mil =
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25.4 mm.
.03937 in.
30.48 cm.
3.28083 ft.
.001 mm.
1 foot
1 yard
1 statute mile
1 nautical mile
0.001 inch
AREA
1 sq. in.
=
1 sq. ft.
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1 sq. cm.
=
1 sq. cm.
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144 sq. inches =
9 sq. feet
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Cross sectional area =
in circular mils
6.4516 sq. cm.
929.03 sq. cm.
0.155 sq. in.
0.0010764 sq. ft.
1 sq. ft.
1 sq. yard
Square of diameter in mils
VOLUME
1 cu. in. 1 cu. ft.
1 cu. ft. 1 cu. ft. 1 cu. ft. 1 British gal.
1 British gal.
1 British gal.
1 liter
1 liter
1 liter
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16.387 cu. cm.
1728 cu. in.
7.4805 U.S. gal.
6.229 British gal.
28.317 liters
1.20094 U.S. gal.
277.3 cu. in.
4.546 liters
61.023 cu. in.
0.03531 cu. ft.
0.2642 U.S. gal.
FLOW
1 cu. ft. per sec. 1 cu. ft. per sec.
1 U.S. Gal. per min.
1 U.S. Gal. per min.
1 cu. cm. Per sec. =
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448.83 gal. per min.
1699.3 liters per min.
0.002228 cu. ft. per sec.
0.06308 liters per sec.
0.0021186 cu. ft. per min.
DENSITY
1 lb. per cu. ft. 1 lb. per cu. ft.
1 kg. per cu. meter
1 g. per cu. cm. =
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16.018 kg. per cu. meter
.0005787 lb. per cu. in.
0.06243 lb. per cu. ft.
0.03613 lb. per cu. in.
PRESSURE
1 in. of water
1 in. of water
1 ft. of water
1 ft of water
1 in. of mercury
1 in. of mercury
1 in. of mercury
1 atmosphere
1 atmosphere
1 atmosphere
1 atmosphere
1 lb. per sq. in.
1 lb. per sq. in.
1 lb. per sq. in.
1 dyne per sq. cm. 1 micron
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0.03613 lb. per sq. in.
0.07355 in. of Hg.
0.4335 lb. per sq. in.
0.88265 in of Hg.
0.49116 lb. per sq. in.
13.596 in. of water
1.13299 ft. of water
14.696 lb. per sq. in.
760 mm. of Hg.
29.921 in. of Hg.
33.899 ft. of water
27.70 in. of water
2.036 in. of Hg.
.0703066 kg. per sq. cm.
.000145 lb. per sq. in.
.00001943 lb. per sq. in.
ENERGY
1B.T.U. 1 erg
1 erg
1 kilowatt hour
1 kilowatt hour
1 kg. calorie
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777.97 ft. lbs.
9.4805 x 10-11 B.T.U.
7.3756 x 10-8 ft. lbs.
2.655 x 106 ft. lbs.
1.3410 h.p.hr.
3.968 B.T.U.
POWER
1 horsepower
1 horsepower
1 horsepower
1 horsepower
1 watt
1 watt
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33,000 ft. lb. per min.
550 ft. lb. per sec.
2,546.5 B.T.U. per hr.
745.7 watts
0.00134 horsepower
44.26 ft lbs. per min.
WEIGHT
1 ounce av .
1 lb. av.
1 gram 1 kg. 1 cu. ft. of water
1 U.S. Gal. Of water
1 cu. in. of water
1 British gal. Of water
1 cu. ft. of air at 60°F. & 1 atm.
16 ounces
2,000 pounds
2,240 pounds
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28.35 g.
453.59 g.
0.03527 oz. av.
2.205 lb. av.
62.425 lb.
8.33 lb.
0.0361 lb.
10.04 lb.
0.08
1 pound
1 short ton
1 long ton
VELOCITY
1 ft. per sec.
=
1 cm. Per sec. =
30.48 cm. per sec.
.032808 ft. per sec.
CIRCULAR MEASURE
60 seconds
60 minutes
360 degrees
90 degrees
11 1/4 degrees
60 seconds
60 minutes
24 hours
365 days
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1 minute
1 degree
1 circle
1 right angle
1 point on the compass
TIME
=
1 minute
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1 hour
1 day
1 year
CONVERSION FACTORS
Atmosphere (standard)
=
29.92 inches of mercury
Atmosphere (standard)
=
14.7 pounds per square inch
1 horsepower =
746 watts
1 horsepower =
33,000 foot-pounds of work per minute
1 British thermal unit =
778 foot-pounds
1 cubic foot =
7.48 gallons
1 gallon
=
231 cubic inches
1 cubic foot of fresh water =
62.5 pounds
1 cubic foot of salt water
=
64 pounds
1 foot of head of water
=
0.434 pounds per square
inch
1 inch of head of mercury
=
0.491 pounds per square inch
1 gallon of fresh water
=
8.33 pounds
1 barrel (oil)
=
42 gallons
1 long ton of fresh water
=
36 cubic feet
1 long ton of salt water
=
35 cubic feet
1 ounce (avoirdupois) =
437.5 grains
THERM-HOUR CONVERSION FACTORS
1 therm-hour
=
1,000,000 B.T.U. Per hour
1 brake horsepower =
2544 B.T.U. Per hour
1 brake horsepower =
2544/100,000 = 0.02544 therm-
hour
1 therm-hour =
100,000/2544 = 39.3082 brake horsepower
(40 hp is close enough)
1 therm-hour
=
100,000/33,475 = 2.9873
(3 hp is close enough)
Example: How many therm-hours in a 100-hp engine?
Answer: 100 x 0.02544 – 2.544 therm-hours.
BOILER HORSEPOWER
1 therm-hour
=
1,000,000 B.T.U. Per hour
1 brake horsepower =
2544 B.T.U. Per hour
1 brake horsepower =
2544/100,000 = 0.02544 therm-hour
1 therm-hour
=
100,000/2544 = 39.3082 brake horsepower
(40 hp is close enough)
1 therm-hour
=
100,000/33,475 = 2.9873
(3 hp is close enough)
Example: How many therm-hours in a 100-hp engine?
Answer: 100 x 0.02544 – 2.544 therm-hours.
WEIGHT OF WATER AT 62o F
1 cu. in.
1 cu. ft.
1 gal. =
=
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0.0361 lb (of water)
62.355 lb.
8.3391 lb
Useful Formulas
Hydraulic data
Feet head (HD) x .434 = Inches water x .0730 =
PSI
in. hg
Inches of mercury x
PSI x 2.31= ft. HD
1.1337 = ft HD
PSI x 27.72 inches HD
ft HD x .8853 = inches
mercury
1gal water = 8.3lbs
1 cu in. of water = .036
= wet in lb.
1gal# 2 oil =7.2lbs
1cu.ft. = 7.48 gal.
1 cu ft = 1728cu inches 1 gal water =2.31 cu
inches
1 cu ft. water = 62.428 A perfect vacuum at sea
lbs/39 deg
level = 29.9 inches of
mercury or 33.95 ft
water
Area data
Pi = 3.1416
circumference =
diameter pi [3.1416]
pi R 2nd =area
ID = circumference x
0.318
Area of Circ = Dia 2nd x
.7854
HVAC/R Useful Formulas
Air changes per hour: CFM X 60 minutes X Area (Volume
in cubic feet) = Air Changes per Hour (ACH)
Btu’s CFM x T differential (approx. 10-15 Degrees
Fahrenheit) x air density (typically 1.085) = Btu’s delivered
Absolute pressure PSIA = Gauge + 14.7 or 0 PSIG =
14.7 (14.7 = 101.3kPa or 15psi = 100kPa)
Roughly 2 inches Hg = 1psi or 20Hg = 10psi and will 23 ft.
IS equivalent for Btu's is the Joule [J]
A joule is a small amount of heat,1000 J's or (KJ) is used
for Refrigeration Formulas.1 kg of water = approx. 1 liter
The amount of heat to raise 1 kg of water 1 degree Celsius
is = 4.187 KJ
Specific heat
Water
Ice
Air
Superheat
Btu's/LB/f
1.0
.50
.24
.47
Latent heat of fusion
Latent heat of vaporization
450 CFM = 1 ton
kj/kg/k
4.187
2.11
C= (f-32)/1.8
F=[C*1.8] +32
roughly
double
1000 Ton = 2000 GPM
1 Ton Refrigeration = a ton of ice melted in 24 hr 2000 x
144 = 288000Btu's /hr
1Kw/hr = 3415 Btu's
1ton = 12000 Btu
1 Btu = 778 ft/lb.
.746 Kw/hr = 1hp hr
1Hp = 1Ton
1kw = 1.34 hp
1 watt 3.413 Btu
1 Kw/hr = 1.34 hp hr